1. Field of the Invention
The invention relates to a composite diaphragm for diaphragm pumps comprises of an elastomer body and a polytetrafluoroethylene (PTFE) coating on the product side. This elastomer body has the shape of a circular dish that comprises an edge of the dish with a clamping area; a bottom; and a flexible section of the diaphragm connecting the edge of the dish with the bottom.
The composite diaphragm is clamped in a diaphragm pump along the side of the edge, whereas the bottom performs lifting movements. The flexible section of the diaphragm is turned inside out with each lifting movement, whereby roll-off movements of the flexible material are observed in a radial section. Technically speaking, the flexible section of the diaphragm can therefore be referred to as a rolling loop in a tech.
2. The Prior Art
When composite diaphragms are used, where the flexible section of the diaphragm is a smooth ring surface and where the PTFE coating contains radial white staining in the form of lines, this indicates the onset of damage to the material. As this damage to the PTFE material progresses, the composite diaphragm loses its chemical resistance to aggressive conveyed media. The development of this damage as described above limits the useful life of the diaphragm.
U.S. Pat. No. 5,349,896 shows a composite diaphragm that has the structure specified above, wherein the flexible section of the diaphragm is stiffened by radial ribs. Such ribs extend from a transition area adjoining the bottom, up to the edge of the dish of the elastomer body. Thus, these ribs make it possible to prevent the damage described above from developing; however, the roll-off property of the flexible section of the diaphragm deteriorates and the resistance to roll-off increases to a considerable extent.